Microstructured Silicon Photodiodes for Bandwidth-Quantum Efficiency Tradeoffs
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Solution Overview
Problem
Conventional silicon photodetectors face limitations in detecting longer optical wavelengths due to increased transparency, leading to low bandwidth and quantum efficiency, necessitating the use of more expensive materials like Germanium and InGaAs, which also suffer from high multiplication noise.
Innovation Solution
The development of a photodetector with a microstructure-enhanced photon absorbing semiconductor region, featuring pillars, holes, or voids arranged in various patterns to increase absorption across a range of wavelengths, including those beyond 850 nm, utilizing silicon or Germanium, and incorporating reverse biasing to enhance absorption through resonance and scattering effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the thickness of the absorption region is increased to improve quantum efficiency at longer wavelengths, then quantum efficiency is improved, but bandwidth decreases
Solution Approach 1:
The absorption region is segmented into multiple discrete microstructures (pillars, holes, or voids) arranged in arrays. This segmentation increases the effective absorption path length through light scattering and resonance effects while maintaining a compact overall thickness, thereby achieving high quantum efficiency without sacrificing bandwidth
Solution Approach 2:
The invention transitions from a planar absorption region to a three-dimensional microstructured absorption region. The microstructures have vertical dimensions that create resonance cavities and scattering centers, effectively increasing the absorption path length in the vertical dimension while keeping the lateral footprint small, thus resolving the bandwidth-QE tradeoff
2Ease of manufacture
If conventional silicon photodetectors are used for longer wavelengths, then manufacturing cost is reduced, but absorption capability deteriorates due to increased transparency
Solution Approach 1:
The invention changes the geometric parameters of the silicon absorption region by introducing microstructures with specific dimensions (height, width, spacing) that are optimized for resonant absorption at longer wavelengths. This parameter transformation enables conventional silicon to absorb longer wavelengths effectively without requiring expensive alternative materials
Solution Approach 2:
The microstructured silicon absorption region creates an effective composite structure where silicon interacts with air or vacuum in the spaces between microstructures. This composite configuration enhances absorption through resonance and scattering while maintaining the low cost advantage of silicon
3Measurement precision
If alternative materials like Germanium or InGaAs are used to detect longer wavelengths, then absorption capability is improved, but multiplication noise increases and manufacturing cost increases
Solution Approach 1:
The invention uses conventional silicon, which is abundant and inexpensive, instead of expensive alternative materials like Germanium or InGaAs. The microstructuring approach enables silicon to achieve performance previously only attainable with costly materials, eliminating both the high material cost and the associated high multiplication noise
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables silicon photodetectors to achieve bandwidths greater than 5 Gb/s with quantum efficiencies of 60% or higher at 850 nm and beyond, while reducing capacitance and noise, thus overcoming the limitations of conventional silicon photodetectors.
Implementation Method 1
utilizing silicon or Germanium, and incorporating reverse biasing to enhance absorption through resonance and scattering effects
Implementation Method 2
utilizing silicon or Germanium, and incorporating reverse biasing to enhance absorption through resonance and scattering effects
Implementation Method 3
a photodetector with a microstructure-enhanced photon absorbing semiconductor region configured to absorb photons from a source signal
Data Source
AI summary
Techniques for enhancing the absorption of photons in semiconductors with the use of microstructures are described. The microstructures, such as pillars and/or holes, effectively increase the effective absorption length resulting in a greater absorption of the photons. Using microstructures for absorption enhancement for silicon photodiodes and silicon avalanche photodiodes can result in bandwidths in excess of 10 Gb/s at photons with wavelengths of 850 nm, and with quantum efficiencies of approximately 90% or more.